U.S. patent application number 14/852748 was filed with the patent office on 2016-03-31 for sensor-equipped display device and method of controlling the same.
This patent application is currently assigned to Japan Display Inc.. The applicant listed for this patent is Japan Display Inc.. Invention is credited to Kohei AZUMI, Hayato KURASAWA, Hiroshi MIZUHASHI.
Application Number | 20160092020 14/852748 |
Document ID | / |
Family ID | 55584364 |
Filed Date | 2016-03-31 |
United States Patent
Application |
20160092020 |
Kind Code |
A1 |
AZUMI; Kohei ; et
al. |
March 31, 2016 |
SENSOR-EQUIPPED DISPLAY DEVICE AND METHOD OF CONTROLLING THE
SAME
Abstract
According to one embodiment, a first substrate includes a gate
line extending in a first direction, a source line extending in a
second direction intersecting the first direction, a switching
element SW which is connected to the gate line and the source line,
and a pixel electrode which is connected to the switching element
SW. The first substrate includes a common electrode which is
opposed to the pixel electrode, and a detection electrode element
Tx necessary for sensing a state of closeness of a conductor
brought externally, that extends parallel to the common electrode
and is formed of a metallic material. By this structure, power
consumption of a drive electrode of an input sensor can be reduced,
and improvement of a drive frequency can be obtained.
Inventors: |
AZUMI; Kohei; (Tokyo,
JP) ; MIZUHASHI; Hiroshi; (Tokyo, JP) ;
KURASAWA; Hayato; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Japan Display Inc. |
Minato-ku |
|
JP |
|
|
Assignee: |
Japan Display Inc.
Minato-ku
JP
|
Family ID: |
55584364 |
Appl. No.: |
14/852748 |
Filed: |
September 14, 2015 |
Current U.S.
Class: |
345/173 ;
345/104 |
Current CPC
Class: |
G06F 3/0445 20190501;
G06F 3/044 20130101; G06F 3/0412 20130101; G06F 3/04166 20190501;
G06F 3/0446 20190501; G09G 3/3655 20130101; G06F 3/0416
20130101 |
International
Class: |
G06F 3/041 20060101
G06F003/041 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 26, 2014 |
JP |
2014-196696 |
Claims
1. A sensor-equipped display device comprising: a first substrate
comprising a gate line extending in a first direction, a source
line extending in a second direction intersecting the first
direction, a switching element which is electrically connected to
the gate line and the source line, and a pixel electrode which is
electrically connected to the switching element; a common electrode
which is opposed to the pixel electrode and extending in the first
direction; and a detection electrode element which extends parallel
to the common electrode, is formed of a metallic material, and is
driven for sensing a state of closeness of a conductor brought
externally.
2. The sensor-equipped display device of claim 1, wherein a second
substrate, which is opposed to the first substrate with a liquid
crystal layer interposed between the first and second substrates,
is opposed to the gate line and the detection electrode element,
and comprises a light-shielding film extending in the first
direction.
3. The sensor-equipped display device of claim 1, wherein the
detection electrode element is positioned in a same layer as a
layer in which the common electrode is arranged.
4. The sensor-equipped display device of claim 1, wherein the
detection electrode element is positioned in a same layer as a
layer in which the pixel electrode is arranged.
5. The sensor-equipped display device of claim 1, wherein a
plurality of detection electrode elements are provided close to
each other and parallel such that they correspond to the common
electrode.
6. The sensor-equipped display device of claim 1, further
comprising: a first driving circuit which supplies a common driving
signal to the common electrode at a time of display driving for
displaying an image by using the pixel electrode; and a second
driving circuit which supplies a sensor driving signal to the
detection electrode element, receives a sensor detection signal
from the detection electrode element, or receives a sensor
detection signal from the detection electrode element after
supplying a sensor driving signal to the detection electrode
element at a time of sensing driving for performing the
sensing.
7. The sensor-equipped display device of claim 6, wherein the first
driving circuit keeps the common electrode at a fixed potential at
the time of sensing driving.
8. The sensor-equipped display device of claim 6, wherein the first
driving circuit switches a state of the common electrode to an
electrically floating state at the time of sensing driving.
9. A method of controlling a display device comprising a first
substrate and a second substrate, the first substrate comprising: a
gate line extending in a first direction, and a source line
extending in a second direction intersecting the first direction; a
switching element which is electrically connected to the gate line
and the source line, and a pixel electrode which is electrically
connected to the switching element; a common electrode which is
opposed to the pixel electrode and extending in the first
direction; and a detection electrode element which extends parallel
to the common electrode, is formed of a metallic material, and is
necessary for sensing a state of closeness of a conductor brought
externally, the second substrate being opposed to the first
substrate with a liquid crystal layer interposed between the first
and second substrates, opposed to the gate line and the detection
electrode element, and comprising a light-shielding film extending
in the first direction, wherein: common electrodes, each
corresponding to the common electrode of the first substrate, are
driven by a first driving circuit for each bundle (or group) of n
electrodes (where n is a positive integer), and detection electrode
elements, each corresponding to the detection electrode element of
the first substrate, are paired with the common electrodes and are
driven by a second driving circuit for each bundle (or group) of n
elements (where n is a positive integer); and when one bundle of
the detection electrode elements is given a drive pulse from the
second driving circuit, the first driving circuit allows a bundle
of the common electrodes corresponding to the one bundle of the
detection electrode elements being driven to be in a floating
state, and fixes the remaining common electrodes at a predetermined
direct-current voltage.
10. The method of controlling the display device of claim 9,
wherein when a pixel signal is written in a region of the pixel
electrode selected by the gate line and the source line, and/or the
written pixel signal is retained, the second driving circuit sets
the detection electrode elements to be at a same direct-current
potential as the common electrode.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from Japanese Patent Application No. 2014-196696, filed
Sep. 26, 2014, the entire contents of which are incorporated herein
by reference.
FIELD
[0002] Embodiments described herein relate generally to a
sensor-equipped display device and a method of controlling the
display device.
BACKGROUND
[0003] Recently, portable devices (smartphones, tablet personal
computers, personal digital assistants, etc.) have become
widespread. Further, the portable device comprises an input sensor
which detects a change in the capacitance. When a user's finger,
for example, is brought close to a surface of a liquid crystal
display panel of the portable device, the input sensor can detect
position information of the user's finger as an operation
input.
[0004] As the input sensor, an in-cell-type sensor which is
incorporated into the interior of a liquid crystal display panel
and an on-cell-type sensor which is disposed on the surface of a
liquid crystal display panel are available.
[0005] In the in-cell-type sensor, a common electrode for liquid
crystal driving (which is formed by indium-tin-oxide (ITO) having
transparency) is used as a detection electrode element which
constitutes the input sensor. Since the common electrode for liquid
crystal driving is used as the detection electrode element of the
input sensor, it is possible to prevent the thickness of the liquid
crystal display panel from being increased and also to reduce the
manufacturing steps for structuring the input sensor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a perspective view which schematically shows the
structure of a display device according to one embodiment.
[0007] FIG. 2 is a plan view showing the positional relationship
among a pixel electrode, a common electrode, and a first detection
electrode element Tx of an input sensor of a display device
according to one embodiment.
[0008] FIG. 3 is a cross-sectional view of a part of a pixel region
shown in FIG. 2, that is, a cross-sectional view taken along line
X-X of FIG. 2.
[0009] FIG. 4 is an illustration for describing the positional
relationship among a common electrode, a first detection electrode
element, and a pixel electrode.
[0010] FIG. 5 is an illustration for describing an example of
driving the common electrode and the first detection electrode
elements Tx(a-i).
[0011] FIG. 6 is a cross-sectional view of a part of a pixel region
according to another embodiment.
[0012] FIG. 7 is a cross-sectional view taken along line X-X of
FIG. 8, for describing the positional relationship between a common
electrode and first detection electrode elements Tx1 and Tx2, of
the embodiment shown in FIG. 8.
[0013] FIG. 8 shows a part of a pixel region as shown in FIG. 2
according to yet another embodiment.
[0014] FIG. 9A is an illustration for describing an example of a
period in which the first detection electrode element is driven in
the above-mentioned embodiment.
[0015] FIG. 9B is an illustration for describing another example of
a period in which the first detection electrode element is driven
in the above-mentioned embodiment.
[0016] FIG. 10 is an illustration for describing the operating
state of the first detection electrode element and the common
electrode in the above-mentioned embodiment.
[0017] FIG. 11 is an illustration for describing an example of
arrangement of first detection electrode elements Tx and second
detection electrode elements Rx of an input sensor according to a
mutual method, and an operation thereof.
[0018] FIG. 12A is an illustration for describing a self-detection
method which can be applied to the display device, and shows the
state in which a detection electrode is charged in the case where
capacitance coupling is not formed between a detection electrode
and a finger.
[0019] FIG. 12B is an illustration for describing the
self-detection method following FIG. 12A, and shows the state of
discharge from the detection electrode.
[0020] FIG. 12C is an illustration for describing the
self-detection method which can be applied to the display device,
and shows the state in which the detection electrode is charged in
the case where capacitance coupling is formed between the detection
electrode and a finger.
[0021] FIG. 12D is an illustration for describing the
self-detection method following FIG. 12C, and shows the state of
discharge from the detection electrode.
[0022] FIG. 13A is a circuit diagram showing an example of a basic
structure which realizes the self-detection method.
[0023] FIG. 13B is an equivalent circuit schematic showing
capacitances shown in FIG. 13A, and shows the state in which a
charge of capacitor Cc is moved to capacitor Cp and capacitance
Cx.
[0024] FIG. 14 is an illustration showing changes in values of
voltage Vx with respect to capacitance Cx shown in FIGS. 13A and
13B by a bar graph, and changes in values of voltage Vc of
capacitor Cc by a line graph.
[0025] FIG. 15 is an example showing the structure of detection
electrode element Tx of the self-detection method.
[0026] FIG. 16 is another example showing the structure of
detection electrode element Tx of the self-detection method.
DETAILED DESCRIPTION
[0027] Various embodiments will be described hereinafter with
reference to the accompany drawings.
[0028] Recently, the size of tablet personal computers, etc., as a
mobile device has been increased, and display elements have been
improved to achieve higher-resolution.
[0029] When the size of the device is increased, the length of a
common electrode is increased, and so is its width as compared to
conventional devices. Accordingly, a parasitic capacitance between,
for example, the common electrode and a signal line is increased. A
resistance of the common electrode is increased, and a resistance
of a metallic interconnect disposed at a frame around a display
area is also increased.
[0030] As a result, a drive frequency of an input sensor may be
lowered. Also, power consumption of the device is increased because
of the increase in the resistance of the interconnection.
[0031] Hence, embodiments described herein aim to provide a
sensor-equipped display device and a method of controlling the
display device, whereby an increase in the parasitic capacitance
and an increase in the interconnect resistance can be reduced, and
as a consequence, power consumption of a drive electrode of the
input sensor and improvement of the drive frequency can be
obtained.
[0032] The input-sensor-equipped display device according to one
embodiment comprises:
[0033] (1) a first substrate comprising a gate line extending in a
first direction, a source line extending in a second direction
intersecting the first direction, a switching element which is
electrically connected to the gate line and the source line, and a
pixel electrode which is electrically connected to the switching
element; a common electrode which is opposed to the pixel electrode
and extending in the first direction; and a detection electrode
element necessary for sensing the state of closeness of a conductor
brought externally (or an operation input), which extends parallel
to the common electrode and is formed of a metallic material;
and
[0034] (2) a second substrate which is opposed to the first
substrate, and the second substrate comprises a light-shielding
layer (which may also be referred to as a light-shielding film)
which is opposed to the gate line and the detection electrode
element, and extends in the first direction.
[0035] In the following, referring to the accompanying drawings,
the sensor-equipped display device and a method of driving the same
according to one embodiment will be described in detail
specifically. In the present embodiment, the display device is a
liquid crystal display device.
[0036] FIG. 1 is a perspective view showing a schematic structure
of a sensor-equipped display device according to one embodiment. In
FIG. 1, a liquid crystal display device DSP comprises, for example,
an active-matrix-type display panel PNL, a drive IC chip IC1 which
drives the display panel PNL (which may also be referred to as a
first IC chip or a drive circuit), a
capacitance-change-sensing-type input sensor (which will be
described later), a touch IC chip IC2 which drives the input sensor
(which may also be referred to as a second IC chip or a sensor
circuit), a backlight unit BL which illuminates the display panel
PNL, a host device (which may also be referred to as a system
control block) HOS, and flexible interconnect substrates FPC1,
FPC2, and FPC3. As described later, the display panel PNL comprises
a first substrate 100 and a second substrate 200, and includes a
liquid crystal layer 300 between the two substrates.
[0037] FIGS. 2 and 3 illustrate examples of a partial plan view and
a partial cross-sectional view of the display panel PNL of the
sensor-equipped display device according to one embodiment.
[0038] FIG. 2 representatively shows four pixel regions PXA1, PXA2,
PXA3, and PXA4 which are arranged two-dimensionally.
[0039] FIG. 2 shows the positional relationship among pixel
electrodes 108, common electrodes 110 (110-1, 110-2, . . . ), and
first detection electrode elements Tx which form the input sensor
to be described later. The first detection electrode element Tx is
an electrode which is necessary for sensing (detecting) the
so-called touch input (the state of closeness of a conductor
brought externally or an operation input).
[0040] The pixel electrodes 108 are disposed two-dimensionally.
Also, in each of the pixel electrodes 108, a plurality of slits SL
are formed so that an electric field for driving liquid crystal
molecules of the liquid crystal layer 300 (FIG. 3) can be formed.
In the display device, as a method for driving the liquid crystal
molecules between the pixel electrode 108 and the common electrode
110, fringe field switching (FFS) or in-plane switching (IPS),
etc., may be adopted.
[0041] Further, FIG. 2 shows a plurality of gate lines 160 (which
may also be referred to as scanning lines) disposed parallel to
each other in a first direction, and a plurality of source lines
150 (which may also be referred to as signal lines) disposed
parallel to each other in a second direction intersecting the first
direction. A set of the pixel electrode 108 and a switching element
(which will be described later) is arranged near an intersection of
the gate line 160 and the source line 150. The switching element is
constituted by, for example a thin-film transistor (TFT).
[0042] Also, the first detection electrode elements Tx which will
be described later are disposed parallel to the common electrodes
110. The first detection electrode elements Tx constitute an
element of the sensor for detecting the so-called touch input.
Preferably, the first detection electrode elements Tx should not be
overlapped with the pixel electrodes in a top view.
[0043] FIG. 3 shows a cross-section of a part of a pixel region, in
particular. FIG. 3 is a cross-sectional view of a liquid crystal
display device including the first substrate 100, the second
substrate 200, the liquid crystal layer 300, and the backlight unit
BL taken along line X-X (FIG. 2). In FIG. 3, 100 represents the
first substrate (which may also be referred to as an array
substrate), and 200 represents the second substrate (which may also
be referred to as a counter-substrate). The first substrate 100 and
the second substrate 200 are opposed to each other with the liquid
crystal layer 300 interposed therebetween.
[0044] In the display panel PNL, the liquid crystal molecules are
subjected to alignment control in accordance with the state of an
electric field, and the light which passes can be modulated. For an
alignment control mode of the liquid crystal molecules, a lateral
electric field mode such as the aforementioned fringe field
switching (FFS) or in-plane switching (IPS) is adopted.
[0045] The second substrate 200 comprises, in the order of
constituent elements from the outer side to the inner side (the
side of the liquid crystal layer 300), a polarization film OD2, a
second detection electrode element Rx for forming the input sensor,
a glass substrate 202, a light-shielding layer 203, a color filter
204, an overcoat layer 205, and an alignment film 206.
[0046] The color filter 204 changes the light which has passed
through the liquid crystal layer 300 into colored light. The
light-shielding layer 203 prevents unnecessary reflected light from
being emitted from a metallic electrode of the switching element or
a metallic interconnect which is disposed in a non-display area to
be described later. The overcoat layer 205 is provided on the inner
side (i.e., the side of the liquid crystal layer) of the color
filter 204, and is intended to modulate the unevenness of the color
filter 204.
[0047] The function and the operation of the second detection
electrode element Rx will be described in detail later together
with the first detection electrode elements provided on the side of
the first substrate 100.
[0048] On the outer side of the first substrate 100 (the lower side
in the drawing), the backlight unit BL is disposed. In the first
substrate 100, in the order of constituent elements from the outer
side to the side of the liquid crystal layer 300, a polarization
film OD1, a glass substrate 101, a first insulating layer 102, a
second insulating layer 103, a third insulating layer 104, a fourth
insulating layer 105, a fifth insulating layer 106, and an
alignment film 107 are disposed.
[0049] The polarization film OD1 of the first substrate 100 and the
polarization film OD2 of the second substrate 200 have the
relationship that the directions of polarization of these
polarization films are orthogonal to each other, for example.
[0050] The first substrate 100 comprises a switching element SW
which employs a semiconductor. Although one switching element SW is
shown as a typical example of the switching elements in the
drawing, a plurality of switching elements are arranged within the
first substrate 100 two dimensionally (i.e., in the first direction
and the second direction which intersects the first direction).
[0051] Each of the switching elements SW comprises a gate electrode
WG, a semiconductor layer WW, a source electrode WS, and a drain
electrode WD. The semiconductor layer WW comprises a channel region
CH at a central position which is opposed to the gate electrode WG,
and a source region SD and a drain region DD on both sides of the
channel region CH. The source region SD is connected to the source
electrode WS, and the drain region DD is connected to the drain
electrode WD.
[0052] The gate electrode WG, the source electrode WS, and the
drain electrode WD are made of metal such as aluminum. The gate
electrode WG is connected to the gate line 160 (FIG. 2) formed on
the glass substrate 101. The insulating layer 102 is provided
between the gate electrode WG and the semiconductor layer WW.
Further, the semiconductor layer WW is disposed between the
insulating layers 102 and 103.
[0053] The source electrode WS is connected to the source region SD
via contact holes of the insulating layers 103 and 104, and the
drain electrode WD is also connected to the drain region DD via
contact holes of the insulating layers 103 and 104.
[0054] The source electrode WS is connected to the source line 150
(FIG. 2), and a write signal (which may also be referred to as a
pixel signal) is supplied from the source line 150. The drain
electrode WD is connected to the pixel electrode 108 via the
insulating layers 105 and 106. The pixel electrode 108 comprises
the slits SL as shown in FIG. 2. The pixel electrode 108 is an
electrode corresponding to the switching element SW.
[0055] In the first substrate 100, a plurality of pixel electrodes
are arranged two-dimensionally such that they correspond to a
plurality of switching elements SW.
[0056] The common electrode 110 is provided on the insulating layer
105, that is, between the insulating layers 105 and 106, and along
one of the arrangement directions of the pixel electrodes. Although
FIG. 3 shows the common electrode 110 corresponding to one of the
pixel electrodes 108, this common electrode also corresponds to the
other adjacent pixel electrode (as shown in FIG. 2). For example,
as shown in FIG. 2, with respect to the pixel electrodes 108, 108,
. . . which are arranged in the first direction, a single common
electrode, i.e., the common electrode 110-1 or 110-2, is disposed.
Accordingly, a plurality of common electrodes, i.e., the common
electrodes 110-1 and 110-2, are arranged in the second direction
intersecting the first direction. The number of common electrodes
110 which are arranged in the second direction intersecting the
first direction is set as appropriate according to the
specification of the display device.
[0057] Further, in the same layer as the layer where the common
electrode 110 is disposed, the first detection electrode element Tx
which constitutes the input sensor to be described layer is formed.
The first detection electrode element Tx is separated from the
common electrode 110, and is disposed along the common electrode
110. The pixel electrode 108 and the common electrode 110 are
transparent electrodes made of ITO, for example.
[0058] In the display panel PNL described above, the gate line 160
is selectively driven by a gate drive circuit not shown. When a
drive voltage is supplied to a predetermined gate line 160, the
switching element SW which is connected to this gate line 160 is in
an on-state. Here, when a write signal is provided to the source
line 150 from a source drive circuit, the signal is written in a
corresponding pixel circuit via the switching element SW which is
in the on-state. The matter that a signal is written means that a
voltage according to a write signal (a pixel signal) is charged and
held between the pixel electrode and the common electrode which
form one pair. As a result, in accordance with the charged voltage,
an electric field that passes through the slits SL of the pixel
electrode is produced between, for example, the pixel electrode 108
and the common electrode 110. By this electric field, liquid
crystal molecules of the liquid crystal layer 300 are driven, and
by this phenomenon, the amount of light that passes through the
liquid crystal layer 300 is controlled.
[0059] FIG. 4 is an illustration for describing the positional
relationship between the common electrode 110 and the first
detection electrode element Tx, and an example of driving these
electrode and element. The example of driving is an example for
driving the common electrode 110 and the first detection electrode
element Tx to be operated as the input sensor. Since FIG. 4
illustrates a plurality of common electrodes and a plurality of
first detection electrode elements, suffixes a, b, c, . . . are
added to the reference numbers.
[0060] The common electrodes 110a, 110b, 110c, . . . can be
controlled per several rows by a first driving circuit (which may
also be referred to as a common electrode control circuit) 500.
FIG. 4 shows a configuration example in which the common electrodes
can be controlled per three rows. For example, by closing switch S1
(to establish an on state) and opening switches S2 and S3 (to
establish an an off state), the first driving circuit 500 can make
the common electrodes 110a to 110c, which are the three electrodes
in the upper part of the drawing, fixed at a constant direct
current (DC) voltage, and allow the remaining common electrodes
110d to 110i to be in a floating state.
[0061] Similarly, the first detection electrode elements Txa to Txi
can also be driven per three rows in synchronization with the
driving of the common electrodes by a second driving circuit (which
may also be referred to as a detection electrode control circuit)
550.
[0062] In the above-described embodiment, a plurality of pixel
electrodes are arranged over each row of a set of the common
electrode and first the detection electrode element in the first
direction. In FIG. 4, reference numbers 108a, 108b, 108c, . . . are
representatively added to the plurality of pixel electrodes in a
row. Pixel electrodes are arranged in the other rows as well.
[0063] FIG. 5 is an illustration for describing the state of an
operation period for acquiring an operation input by driving the
first detection electrode elements. The first detection electrode
elements Txa, Txb, and Txc are driven by applying a drive pulse (a
driving signal) of a predetermined frequency for a certain period.
At this time, switch S1 is opened (i.e., to establish an off state)
to allow the common electrodes 110a, 110b, and 110c corresponding
to the first detection electrode elements Txa, Txb, and Txc to be
in the floating state, and the remaining common electrodes 110d to
110i are made to have a fixed potential as a result of being
applied a direct-current voltage. Consequently, by the effect of
the first detection electrode elements Txa, Txb, and Txc which are
being driven, it is possible to prevent the potential of the other
common electrodes 110d to 110i from being varied, and an image
display state (which may also be referred to as a retention state)
from being adversely affected.
[0064] As described above, the first detection electrode elements
in units of three rows, for example, are sequentially driven by the
drive pulse, whereby the corresponding common electrodes in units
of three rows are sequentially controlled to be in the floating
state in synchronization with this driving, and the remaining
common electrodes are controlled to have a fixed potential by a
direct-current voltage. Note that the driving in units of three
rows is only an example, and the number of rows is not limited.
[0065] As described above, in a period of driving the first
detection electrode elements Tx which constitute the input sensor,
a group of common electrodes which are in the floating state and a
group of common electrodes whose potential is fixed by a
direct-current voltage exist.
[0066] With the above structure, by forming the first detection
electrode elements Tx as an interconnect made of a metallic
material such as aluminum, low-resistance can be realized.
Accordingly, it is possible to prevent the drive frequency of the
input sensor from being lowered. Also, it is possible to reduce the
width of the interconnect working as the first detection electrode
elements Tx, and a parasitic capacitance can also be reduced. As a
result, overall power consumption reduction can also be
achieved.
[0067] It should be noted that various embodiments can be adopted
for driving the common electrodes and driving the first detection
electrode elements by the first driving circuit 500 and the second
driving circuit 550.
[0068] At the time of display driving for displaying an image by
using the pixel electrodes (i.e., in a display period), the first
driving circuit 500 supplies common driving signals to the common
electrodes. Also, at the time of sensing driving in which a sensor
performs the sensing, the second driving circuit 550 can supply
sensor driving signals to the detection electrode elements, receive
sensor detection signals from the detection electrode elements, or
receive sensor detection signals from the detection electrode
elements after supplying sensor driving signals to the detection
electrode elements.
[0069] The operation of receiving the sensor detection signals from
the detection electrode elements after the sensor driving signals
have been supplied to the detection electrode elements by the
second driving circuit 550 may be performed at the time of
self-sensing to be described later.
[0070] Further, the first driving circuit 500 may keep the common
electrodes at a fixed potential at the time of sensing driving.
Furthermore, the first driving circuit 500 can switch the state of
the common electrodes to an electrically floating state at the time
of sensing driving. Alternatively, if a structure in which all of
the common electrodes can be switched between the fixed potential
state and the floating state, a circuit size of the first driving
circuit can be reduced.
[0071] FIG. 6 shows another embodiment in which two detection
electrode elements Tx1 and Tx2 are arranged for one common
electrode. That is, the arrangement of first detection electrode
elements Tx is not limited in such a way that one electrode is
provided for one common electrode. Since the other constituent
features are the same as those described in the part referring to
FIG. 3, explanations of them will be omitted.
[0072] When the two first detection electrode elements Tx1 and Tx2
are arranged for one common electrode as described above, a
capacitance for detecting the operation input can be increased.
[0073] FIG. 7 shows yet another embodiment in which first detection
electrode element Tx is arranged in the same layer as the layer
where pixel electrode 108 is disposed. The layer in which the first
detection electrode element Tx is disposed is not limited to the
same layer as the layer in which the common electrode 110 is
disposed. Even in the case where the first detection electrode
element Tx is arranged in the same layer as the layer in which the
pixel electrode 108 is disposed, the first detection electrode
element Tx is arranged such that it forms a pair with the common
electrode in order to enable the control described with reference
to FIG. 5.
[0074] FIG. 8 shows the positional relationship between the first
detection electrode element Tx and the common electrode 110 when
the first detection electrode element Tx is arranged in the same
layer as the layer in which the pixel electrode 108 is disposed.
When the first detection electrode element Tx is arranged in the
same layer as the layer in which the pixel electrode 108 is
disposed, the first detection electrode element Tx is arranged
between the switching element SW and the adjacent pixel electrode,
as seen in a planar view. That is, as shown in FIG. 8, first
detection electrode element Tx-1 is paired with common electrode
110-1, and first detection electrode element Tx-2 is paired with
common electrode 110-2.
[0075] FIG. 9A is an illustration for describing an example of a
period in which the detection electrode elements are driven in the
above embodiment. FIG. 9B is an illustration for describing another
example of a period in which the detection electrode elements are
driven in the above embodiment.
[0076] In a timing chart of FIG. 9A, in one frame period T1F, image
signal write period TM is set for a period from start time t1 to
time t2. For a period from time t2 to time t3, period TD for
reading a sensor detection signal from the sensor is set. In a
pixel circuit, the row in which signal writing is not performed and
from which the sensor detection signal is not read is in a
retention state in which a written image signal is retained. In the
retention state (which may also be referred to as a display state
of the pixel circuit), the common electrodes are kept at a constant
direct-current voltage.
[0077] In the example of a timing chart of FIG. 9B, in one frame
period, image signal write periods TM1, TM2, . . . , TMn, and
periods TD1, TD2, . . . , TDn for reading sensor detection signals
are set in a time-sharing manner. Also in this case, in the pixel
circuit, the row in which writing of an image signal is not
performed and from which a sensor detection signal is not read is
in the retention state (the display state) of the image signal.
[0078] FIG. 10 shows the state of the common electrodes in the
image signal write periods (or the display periods) and the sensor
driving periods (i.e., sensor detection signal read periods) in the
timing chart shown in FIG. 9B. Also, this figure is an explanatory
diagram illustrating the state in which driving signals are given
to the detection electrode elements.
[0079] That is, in this device, common electrodes 110FL, 110FL, . .
. corresponding to the first detection electrode elements Tx being
driven are controlled to be in the floating state. Common
electrodes 110DC, 110DC, . . . corresponding to the first detection
electrode elements Tx not being driven are fixed at a constant
direct-current (DC) voltage. Also, when the first detection
electrode elements Tx are driven, they are given a drive pulse (Tx
driving signal) of a predetermined frequency, and at times other
than that, they are given a constant direct-current (DC)
voltage.
[0080] The driving as described above is carried out by the first
driving circuit 500 and the second driving circuits 550 shown in
FIGS. 3 and 4.
[0081] FIG. 11 is an illustration for further describing a basic
structure and the operation of the sensor. As described above, in
the first substrate 100, the common electrodes 110a, 110b, . . . ,
and the first detection electrode elements Txa, Txb, . . . are
disposed. Also in the second substrate 200, second detection
electrode elements Rx1, Rx2, . . . , Rxn are provided. The second
detection electrode elements Rx1, Rx2, . . . , Rxn are made of a
transparent material, such as ITO, and can form a capacitance with
the counterpart first detection electrode elements Txa, Txb, . . .
, etc. Rxs1, Rxs2, . . . , Rxs(n-2), Rxs(n-1), Rxsn are detection
signals which are output from the second detection electrode
elements Rx1, Rx2, . . . , Rxn.
[0082] Here, when an external conductor such as a finger 35 is
brought close, the capacitance between the opposed detection
electrode elements is changed. A coordinate position of the changed
capacitance is specified as the change in the sensor detection
signals Rxs1 Rxs2, . . . , etc., which are output from the second
detection electrode elements Rx1, Rx2, . . . , Rxn is determined by
the touch IC chip IC2 (FIG. 1).
[0083] For example, it is assumed that the finger 35 is brought
close to a position indicated by a circle 36 in FIG. 11. In this
case, when the detection electrode elements Txa and Txb are driven,
for example, an amplitude of the sensor detection signals Rxs(n-1)
and Rxsn from the detection electrode elements Rx(n-1) and Rxn is
decreased as compared to the case where the finger is not brought
close.
[0084] The touch IC chip IC2 (FIG. 1) which controls (includes) the
first driving circuit (the detection electrode control circuit) 550
shown in FIGS. 4 and 5 can receive the sensor detection signals
Rxs1 to Rxsn as well as driving the first detection electrode
elements Tx. Accordingly, the coordinate position of the changed
capacitance can be determined by the touch IC chip IC2 on the basis
of the driving timing of the first detection electrode elements
Txa, Txb, . . . , and the change in the sensor detection signals
Rxs1 Rxs2, . . . , etc., which are output from the second detection
electrode elements Rx1, Rx2, . . . , Rxn.
[0085] Further, in FIGS. 3, 6, 7, etc., while the second detection
electrode element Rx is disposed between the polarization film OD2
and the glass substrate 202 in the second substrate (the
counter-substrate), the position is not limited to this and the
second detection electrode element Rx can be disposed as
appropriate in the other layers as long as it is closer to the side
of the user's view than the first detection electrode elements Tx
are.
[0086] FIGS. 12A to 16 are illustrations for describing an example
of the other basic structures and operations of the sensor. The
detection electrode elements Txa, Txb, Txc . . . , described above
can also be used as self-detection electrodes.
[0087] A principle of a self-detection method will be described.
The self-detection method uses, for example, capacitance Cx1 that
the detection electrode element Tx has. Also, the self-detection
method uses Cx2 which is produced by the user's finger, etc., that
is close to the detection electrode element Tx.
[0088] FIGS. 12A and 12B represent the state in which the user's
finger is neither brought into contact with nor brought close to an
upper surface of the display panel. Accordingly, capacitance Cx2 is
not produced between the detection electrode element Tx and the
finger. FIG. 12A shows the state in which a power source Vdd and
the detection electrode element Tx is connected by a control switch
SWc. FIG. 12B shows the state in which the power source Vdd and the
detection electrode element Tx are disconnected by the control
switch SWc, and the detection electrode element Tx is connected to
a capacitor Cpp.
[0089] In the state of FIG. 12A, capacitance Cx1 is charged, and in
the state of FIG. 12B, capacitance Cx1 is discharged. Here, the
matter that capacitance Cx1 is charged means that a constant write
signal is written in the detection electrode element Tx. Also, the
matter that capacitance Cx1 is discharged means that a signal which
indicates a change in the capacitance produced in the detection
electrode element Tx is read. The write and read signals described
above are output and read from the second driving circuit 550 shown
in FIGS. 4 and 5.
[0090] Meanwhile, FIGS. 12C and 12D represent the state in which
the user's finger is brought into contact with or brought close to
the upper surface of the display panel PNL. Accordingly,
capacitance Cx2 is produced between the detection electrode element
Tx and the finger. FIG. 12C shows the state in which the power
source Vdd and the detection electrode element Tx is connected by
the control switch SWc. FIG. 12D shows the state in which the power
source Vdd and the detection electrode element Tx are disconnected
by the control switch SWc, and the detection electrode element Tx
is connected to a capacitor Ccp.
[0091] In the state of FIG. 12C, capacitance Cx1 is charged, and in
the state of FIG. 12D, capacitance Cx1 is discharged.
[0092] Here, voltage change characteristics of capacitor Ccp at the
time of discharging shown in FIG. 12D are apparently different from
those at the time of discharging shown in FIG. 12B because of the
presence of capacitance Cx2. Accordingly, in the self-detection
method, input position information (for example, whether an
operation input has been made) is determined by utilizing the
feature that the voltage change characteristics of capacitor Cpp
differ depending on the presence or absence of capacitance Cx2.
[0093] FIG. 13A shows an example of a basic circuit which realizes
the self-detection method. This circuit is provided in the touch IC
chip IC2 shown in FIG. 1, for example.
[0094] As shown in FIG. 13A, the detection electrode element Tx is
connected to one of terminals of capacitor Cp for dividing a
voltage, and also to one of input terminals of comparator COMP. The
detection electrode element Tx has capacitance Cx of its own. The
other one of the input terminals of comparator COMP is connected to
a terminal which supplies comparison voltage Vref.
[0095] The other one of the terminals of capacitor Cp is connected
to a power source line for voltage Vcc via switch SW1. Further, the
other one of the terminals of capacitor Cp is connected to one of
terminals of capacitor Cc via resistor Rc. The other one of the
terminals of capacitor Cc is connected to a reference potential
(for example, a ground potential).
[0096] Switch SW2 is connected between the other one of the
terminals of capacitor Cp and the reference potential, and switch
SW3 is connected between the one of the terminals of capacitor Cp
and the reference potential. Switches SW1, SW2, and SW3, and
comparator COMP are provided within a control circuit inside the
touch IC chip IC2.
[0097] Next, the operation will be described. Switch SW1 is closed
(to establish an on state) at a predetermined cycle to allow
capacitor Cc to be charged. When capacitor Cc is charged, switches
SW2 and SW3 are opened (to establish an off state). When capacitor
Cc is completely charged, all of switches SW1, SW2, and SW3 are
opened and a charge in capacitor Cc is maintained.
[0098] Next, switches SW2 and SW2 are closed (to establish an on
state) for a predetermined length of time (and switch SW1 is kept
open so that an off state is maintained). When the switches are
operated in this way, most of the charges in capacitor Cp and
capacitance Cx is released, and a part of the charge in capacitor
Cc is released via resistor Rc.
[0099] Next, switches SW1, SW2 and SW3 are all opened (to establish
an off state). Then, the charge in capacitor Cc is moved to
capacitor Cp and capacitance Cx. An equivalent circuit at this time
can be represented as illustrated in FIG. 13B. After that, voltage
Vx with respect to capacitance Cx is compared with comparison
voltage Vref or threshold voltage Vth in comparator COMP.
[0100] As shown in the equivalent circuit of FIG. 13B, when all of
switches SW1, SW2, and SW3 are opened (to establish an off state),
the charge in capacitor Cc is moved to capacitor Cp and capacitance
Cx, and then, a change in voltage Vx with respect to capacitance Cx
is compared with comparison voltage Vref in comparator COMP. The
operation as described above is repeated until the voltage
satisfies the relationship Vx<Vref.
[0101] That is, after charging in capacitor Cc has been executed,
switches SW2 and SW3 are closed (to establish an on state) for a
predetermined length of time (and switch SW1 is kept open so that
an off state is maintained). Then, most of the charges in capacitor
Cp and capacitance Cx are released, and a part of the charge in
capacitor Cc is released via resistor Rc. Next, switches SW1, SW2
and SW3 are all opened (to establish an off state). Then, the
charge in capacitor Cc is moved to capacitor Cp and capacitance
Cx.
[0102] The relationship between voltages Vp, Vc, and Vx and
capacitors Cp and Cc and capacitor Cx can be represented by
equations (1) to (3) given below.
Vc=Vp+Vx (1)
Vp:Vx=(1/Cp):(1/Cx) (2)
Vx=(Cp/Cp+Cx)).times.Vc (3)
[0103] As described above, after capacitor Cc has been charged up
to voltage Vc via switch SW1, when opening and closing of switches
SW2 and SW3 is repeated while switch SW1 is kept open, voltage Vc
of capacitor Cc is gradually lowered and voltage Vx with respect to
capacitance Cx is also lowered. This operation, that is, the
operation of repeating the opening and closing of switches SW2 and
SW3 after capacitor Cc is charged to voltage Vc, is continued until
voltage Vx becomes less than comparison voltage Vref.
[0104] FIG. 14 shows examples of a waveform of change in voltage Vc
of capacitor Cc, and an output waveform of comparator COMP. The
horizontal axis represents time and the vertical axis represents
voltage.
[0105] When switch SW1 is closed (to establish an on state),
capacitor Cc is charged to voltage Vcc. After that, all of switches
SW1, SW2, and SW3 are opened (to establish an off state), and the
charge of capacitor Cc is moved to capacitor Cp and capacitance Cx.
Next, a change in voltage Vx with respect to capacitance Cx is
compared with comparison voltage Vref in comparator COMP.
[0106] The characteristics of the change in voltage Vc or the
degree of the change is varied according to a total value of
capacitor Cp and capacitance Cx. Also, the change in capacitor Cc
has an influence over voltage Vx with respect to capacitance Cx.
Further, the value of capacitance Cx is varied according to the
degree of closeness of the user's finger to the detection electrode
element Tx.
[0107] Accordingly, as shown in FIG. 14, when the finger is far
from the detection electrode element Tx, the characteristics
correspond to VCP1 which involves a gradual change, and when the
finger is close to the detection electrode element Tx, the
characteristics correspond to VCP2 which involves a rapid change.
The reason why a decreasing rate of Vc is greater when the finger
is close to the detection electrode element Rx than when it is far
is because the value of capacitor Cc has been increased by the
capacitance of the finger.
[0108] Comparator COMP compares voltage Vp with comparison voltage
Vref or threshold voltage Vth in synchronization with the opening
and closing of switches SW2 and SW3 repetitively. Further, when
Vp>Vref, comparator COMP obtains an output pulse. However,
comparator COMP stops obtaining the output pulse when
Vp<Vref.
[0109] The output pulse of comparator COMP is monitored by a
measurement circuit, not shown, within the touch IC chip IC2 or a
measurement application. That is, after performing the charging in
capacitor Cc once, repetitive discharge by switches SW1 and SW2
mentioned above for a short period of time is executed and a value
of voltage Vp is repetitively measured.
[0110] At this time, a period for obtaining the output pulse of
comparator COMP (MP1 or P2) may be measured, or the number of
output pulses of comparator COMP (i.e., the number of pulses after
capacitor Cc has been charged to the time when Vref becomes greater
than Vp (Vp<Vref)) may be measured.
[0111] When the finger is far from the detection electrode element
Tx, the period is long, and when the finger is close to the
detection electrode element Tx, the period is short. Alternatively,
when the finger is far from the detection electrode element Tx, the
number of output pulses of comparator COMP is large, and when the
finger is close to the detection electrode element Tx, the number
of output pulses of comparator COMP is small. Accordingly, the
degree of closeness to a planar surface of the sensor can be
determined by the number of detection pulses.
[0112] Next, in order to detect the position of a finger which
touches the planar surface of the sensor two-dimensionally, the
detection electrode elements Tx are arranged two-dimensionally (in
matrix), thereby enabling the position of the finger which touches
the planar surface of the sensor to be detected. As described
above, although whether the user's finger has an effect on the
detection electrode element Tx is detected, the time for that
detection is on the order of several tens of .mu.m to several
ms.
[0113] However, the self-detection method used in the present
embodiment is not necessary used for the purpose of detecting the
position of a finger which touches the planar surface of the sensor
two-dimensionally.
[0114] For example, by the second driving circuit 550 (FIG. 4), the
detection electrode elements Txa, Txb, Txc, . . . are bundled per
several rows (for example, three to five rows), and the detection
electrode elements for each bundle is controlled for self-detection
operation. When this self-detection operation is performed, the
second driving circuit 550 can detect on which group of rows (i.e.,
the bundle) the touching finger is positioned. Alternatively, the
second driving circuit 550 can detect from which group of rows
(i.e., the bundle) the touching finger has moved, and to which
group of rows (i.e., the bundle) the touching finger has moved.
[0115] The self-detection function described above can be utilized
when an operation input of simply scrolling an image in the second
direction (upward or downward), for example, is required.
Alternatively, the self-detection function described above can be
utilized in detecting in which way of the second direction (upward
or downward) the touching finger has moved, for example.
[0116] FIG. 15 shows a configuration example of detection electrode
elements that can be adapted in both the self-detection method and
a mutual detection method. In the operation of a self-detection
method, the detection element electrodes Tx1 to Txn are mainly
used. In the first substrate (which may also be referred to as the
array substrate), a plurality of detection electrode elements Txa,
Txb, Txc, . . . are disposed in the first direction. In the second
substrate (which may also be referred to as the counter-substrate),
a plurality of detection electrode elements Tx1 to Txn (transparent
electrodes) are disposed along the second direction intersecting
the first direction. All of the detection electrode elements Txa,
Txb, Txc, . . . , and Tx1 to Txn can be driven, and a change in the
potential of the detection electrode elements Tx1 to Txn is
detected.
Accordingly, the detection electrode element Rx does not need to be
provided within the second substrate (the counter-substrate) 200.
An amount of the change in the potential when a finger is brought
close to a region 37 shown in FIG. 15 at the time of driving the
detection electrode elements Txb and Tx (n-2) is different from
that when the finger is not close, as indicated in, for example,
FIGS. 12A to 12D and FIG. 13A. Note that the detection electrode
elements Txa, Txb, Txc, . . . , and Tx1 to Txn may be bundled by an
arbitrary number to perform the driving and the detection.
[0117] FIG. 16 shows another example of a configuration of the
detection electrode elements Tx of the self-detection method. In
the first substrate (which may also be referred to as the array
substrate), a plurality of detection electrode elements Txa1 to
Txan, Txb1 to Txbn, Txc1 to Txcn . . . are disposed along the
common electrodes 110a, 110b, 110c, . . . , etc. Driving and
detection is separately conducted in each of the detection
electrode elements Txa1 to Txan, Txb1 to Txbn, Txc1 to Txcn, . . .
, etc. Accordingly, a region near the finger can be detected with
high accuracy. Also, the detection electrode element Rx does not
need to be provided within the second substrate (the
counter-substrate) 200. An amount of the change in the potential
when a finger is brought close to a region 38 shown in FIG. 16 at
the time of driving the detection electrode element Txb1 is
different from that when the finger is not close, as indicated in,
for example, FIGS. 12A to 12D and FIG. 13A. Note that the detection
electrode elements Txa1 to Txan, Txb1 to Txbn, Txc1 to Txcn, . . .
, may be bundled by an arbitrary number to perform the driving and
the detection.
[0118] In one aspect, the above embodiment can be described as
follows:
[0119] A first substrate comprises a gate line extending in a first
direction, a source line extending in a second direction
intersecting the first direction, a switching element which is
electrically connected to the gate line and the source line, and a
pixel electrode which is electrically connected to the switching
element. Further, a common electrode is opposed to the pixel
electrode, and extends in the first direction. Furthermore, a
detection electrode element necessary for sensing the state of
closeness of a conductor which brought externally extends parallel
to the common electrode, and is formed of a metallic material.
[0120] Also, a second substrate is opposed to the first substrate
with a liquid crystal layer interposed between the first and second
substrates, and comprises a light-shielding layer (which may also
be referred to as a light-shielding film) which is opposed to the
gate line and the detection electrode element, and extends in the
first direction.
[0121] In addition, common electrodes, each corresponding to the
above-described common electrode, are connected to a first driving
circuit for each bundle (or group) of n electrodes (where n is a
positive integer), and detection electrode elements, each
corresponding to the above-described detection electrode element,
are paired with the common electrodes, and connected to a second
driving circuit for each bundle (or group) of n elements (where n
is a positive integer), in which when one bundle of the detection
electrode elements is given a drive pulse from the second driving
circuit, the first driving circuit allows a bundle of the common
electrodes corresponding to the one bundle of the detection
electrode elements being driven to be in a floating state, and
fixes the remaining common electrodes at a predetermined
direct-current voltage.
[0122] Moreover, when a pixel signal is written in a region of the
pixel electrode selected by the gate line and the source line,
and/or the written pixel signal is retained, the second driving
circuit can set the detection electrode elements to be at the same
direct-current potential as the common electrodes.
[0123] Further, at the time of display driving for displaying an
image by using the pixel electrode, the first driving circuit 500
can supply common driving signals to the common electrodes.
Furthermore, at the time of sensing driving in which the sensing is
performed, the second driving circuit 550 can supply sensor driving
signals to the detection electrode elements, receive sensor
detection signals from the detection electrode elements, or receive
sensor detection signals from the detection electrode elements
after supplying sensor driving signals to the detection electrode
elements.
[0124] In another aspect, the above embodiment can be described as
follows:
[0125] A first substrate comprises the gate line, the source line,
the switching element, the pixel electrode, the common electrodes,
and the detection electrode elements. Here, the common electrodes
are driven by the first driving circuit for each bundle (or group)
of n electrodes (where n is a positive integer), and the detection
electrode elements are paired with the common electrodes and are
driven by the second driving circuit for each bundle (or group) of
n elements (where n is a positive integer). Further, when one
bundle of the detection electrode elements is given a drive pulse
from the second driving circuit, the first driving circuit allows a
bundle of the common electrodes corresponding to the one bundle of
the detection electrode elements being driven to be in a floating
state, and fixes the remaining common electrodes at a predetermined
direct-current voltage.
[0126] Here, furthermore, when a pixel signal is written in a
region of the pixel electrode selected by the gate line and the
source line, and/or the written pixel signal is retained, the
second driving circuit may set the detection electrode elements to
be at the same direct-current potential as the common
electrodes.
[0127] In another aspect, the above embodiment can be described as
follows:
[0128] That is, the above embodiment relates to a display device
having the following features: [0129] (a1) The display device
comprises: a first substrate comprising a first layer in which a
plurality of pixel electrodes to which switching elements are
connected, respectively, are arranged two-dimensionally; a second
substrate which is opposed to the first substrate with a liquid
crystal layer interposed between the first and second substrates,
and comprises a plurality of light-shielding films which are
opposed to the arrangement of the switching elements in a
predetermined direction; and a common electrode which is arranged
in either the first substrate or the second substrate in order to
form a driving electric field for driving liquid crystals of the
liquid crystal layer in cooperation with the plurality of pixel
electrodes, and is characterized in that the first substrate is a
non-display area, and an electrode of a metallic interconnect which
constitutes the input sensor is disposed in the predetermined
direction of arrangement of the switching elements in a region
opposed to the plurality of light-shielding films.
[0130] (a2) Further, the common electrode is disposed relative to
the pixel electrode of the first substrate via an insulating layer,
and the electrode of the metallic interconnect is formed in the
first layer likewise the common electrode.
[0131] (a3) Alternatively, the common electrode is disposed
relative to the pixel electrode of the first substrate via an
insulating layer, and the electrode of the metallic interconnect is
formed in the same layer as the layer where the pixel electrode is
formed.
[0132] (a4) Further, a width of the common electrode having a shape
of a band corresponds to a width of one pixel.
[0133] (a5) Further, electrodes of metallic interconnects disposed
between the band-like common electrodes are separated in groups,
and the electrodes of the metallic interconnects of each group
establish common connection.
[0134] (a6) Further, the non-display area in which the electrodes
of the metallic interconnects are disposed is opposed to the
positions of electrodes of the switching elements which constitute
a pixel circuit.
[0135] A display device having a backlight and a liquid crystal
layer has been described as the above embodiment. However, needless
to say, a concept of this invention is also applicable to a display
device comprising a light-emitting element (for example, an organic
EL element).
[0136] While certain embodiments have been described, these
embodiments have been presented by way of example only, and are not
intended to limit the scope of the inventions. Indeed, the novel
embodiments described herein may be embodied in a variety of other
forms; furthermore, various omissions, substitutions and changes in
the form of the embodiments described herein may be made without
departing from the spirit of the inventions. The accompanying
claims and their equivalents are intended to cover such forms or
modifications as would fall within the scope and spirit of the
inventions.
* * * * *